As all other Southeast Asian equity markets slipped yesterday on Indonesian concerns, Jakarta's lead index managed to end firmer as traders exploited arbitrage opportunities opened up by the currency turmoil. Brokers said that as the rupiah slumped, traders pushed up leading Indonesian firms with American depositary receipts (ADRs) or strong US dollar earning streams. The Jakarta Composite Index rose 2.13 per cent to 457.708 points, while the rupiah plunged up to 24 per cent to 10,750 to the US dollar before ending at 9,700. Government plans for a currency board in defiance of the International Monetary Fund, outbreaks of rioting and social unrest and rising political tensions have roiled the country's financial markets in recent days. Brokers said shares in Telekomunikasi Indonesia (Telkom) and Indosat led the market higher yesterday, however, as traders continued to sell their New York-listed ADRs in favour of their cheaper rupiah-denominated domestically listed shares. ADRs are receipts for shares of foreign-based companies held in a US bank vault, entitling the holder to all dividends and capital gains. These large-cap counters dominate the index, with Telkom accounting for 16.18 per cent of its weighting and Indosat 6.73 per cent. Brokers said other big gainers in recent weeks had included tin miner Tambang Timah and paper-maker Indah Kiat Pulp & Paper, which have foreign listings but have also been in favour because a major part of their earnings is in dollars. Schroders Sassoon investment analyst Helen Teng said: 'People aren't buying for the sake of [rupiah] earnings any more. They are only playing stocks that are dollar-earners or non-dollar earners depending on the latest currency sentiment.' ING Barings, in a recent report on the market's movements, said that just five companies - Telkom, Indah Kiat, Indosat, Tambang Timah and cigarette-maker Gudang Garam - had accounted for 63 per cent of the market's rebound from its low of 343 points last month to 535 points early last week. 'It seems that many investors see [Gudang] as a major winner should there be inflation as it would be able to raise its prices, therefore profits, dramatically,' ING Barings research head Tom Inglis said. '[It is] a view to which we do not subscribe.' The bulk of other firms listed on the exchange fell yesterday as the country's escalating problems undermined sentiment. 'With that possibility [IMF pull-out] you think that they would not let it happen. But you don't know. It's on the brink of absolutely falling apart,' one Jakarta-based broker said. 'I am the only expatriate left in the office.' The IMF has threatened to withhold bailout payments agreed under the US$43 billion package negotiated last year if the government pushes through the plan for a currency board. Most analysts have condemned the proposal, saying that it could threaten the shaky financial system with higher interest rates. 'The market is sceptical on [central] Bank Indonesia's willingness to forego the lender-of-last-resort role,' ANZ Investment Bank research chief Daniel Lian said. 'Further, the market is not convinced that there will be no interference in the currency board system to benefit [Suharto] family members and corporate cronies.'